Savannah had glimpsed movement right from the corner of her eye just before the machine lurched lightly beneath her. Fortunately, Savannah had been "climbing a hill" rather than running as quickly as she could, and so the bump was more distracting than potentially dangerous. She fingered the pause button, plucking the headphone out of the ear nearest the girl.
Because the form she had seen from the corner of her eye had been lower to the floor than your average adult, she had assumed it was a child, and the bump made her worry that the child had fallen. The sight of the girl in the wheelchair was completely unexpected, however, and Savannah at once felt that, somehow, she was at fault.
"Are you okay?" she asked, though, of course, it was clear that she was.